1. Field of the Invention
The present invention relates generally to duct connectors for aircraft, and specifically to adjustable duct connectors.
2. Description of the Prior Art
With the advent of modern aircraft, the need developed for flexible joint ducting to transport high pressure, high temperature gases, often termed the "bleed air", from the aircraft engine, particularly from a cantilever mounted engine under heavy loads. The temperature differential to which the engine and ducting is subjected, before and after the engine warms up, is approximately 1200 to 1300 degrees Fahrenheit, causing the ducting to undergo considerable thermal growth. In addition, the gravitional forces upon take off, and during vertical climbs, aircraft vibrations and the high pressure operating condition also require a connector which has angular flexibility to prevent breakage from fatigue. Military aircraft, particularly, are subjected to heavy loading such that it is desirable that the ducting have flexible connections.
Flexible ball joints have been disclosed which include spherically concave portions which serve as a socket and a spherically convex portion serving as a ball resting inside the socket. A joint of this type is shown in Affa, U.S. Pat. No. 4,165,107. While serving its intended purpose, a joint of this type suffers the shortcoming that the ball sliding against the socket surface creates a large amount of friction, thus causing substantial premature wear of the components.
Other universal joints have been proposed wherein extensions are pivotally connected to sealing rings by bolts on the interior of aircraft ducting. A joint of this type is shown in Affa, U.S. Pat. No. 3,907,337. However, such a joint suffers the shortcoming that its movement is not sufficiently limited and each pivotal connection is subject to premature fatigue and failure of the joint due to the bending movement and single sided shear force, at the bolt. In addition, substantial friction is created between the spacer rings and the connecting member which serves as a seal causing premature failure of the seal. Moreover, as gases flow through the joint, turbulence is created by the protruding ends of the bolt which form the pivotal connection to the sealing rings.